TM 9-4120-357-14
CHAPTER 2
OPERATING INSTRUCTIONS
Section I. DESCRIPTION AND USE OF OPERATOR'S CONTROLS AND INDICATORS
2-1. Front Control Panel.(See Figure 2-1)
The control panel is located in the upper left quadrant of the front access panel. A rotary switch and a thermostat are
mounted side by side on the panel. The left-hand rotary switch knob operates a five-position mode selector switch. The
right-hand knob operates a continuously variable temperature control thermostat. Normally, all operations of the air con-
ditioner are controlled by the switch and thermostat. Operating position of the selector switch, and their functions are as
follows:
a. Off. All functions.
c. Cool. The ventilating system and the refrigeration system operate automatically.
d. Lo heat. The ventilating system and three of the six heating elements operate under thermostatic control.
e. Hi heat. The ventilating system and all six heating elements operate. Three elements continuously and three un-
der thermostatic control.
2-2. Dampers and Grilles.
Control of air direction and volume is achieved by proper setting of the various dampers and grilles incorporated in the
air conditioner. The function of each of these is described in the following paragraphs:
a. Evaporator discharge grille. (See Figure 1-1) The evaporator discharge grille is located at the top of the front
face of the air conditioner, and extends across the entire width of the unit. Each side of the grille is equipped with adjust-
able vanes to direct the airflow from the ventilating blower. These vanes should always be kept open when the air condi-
tioner is operating in any mode, so that the output of the air will not be obstructed. When the air conditioner is operating
in the cooling mode, the delivered air will be denser that the room air, and will have a tendency to sink downward. To
offset this tendency, the grille vanes should be directed slightly upward. When heating, the delivered air will be less
dense, and will have a tendency to float upward. This tendency may be offset by directing the grilles downward.
b. Evaporator intake grilles. (See Figure 1-1). The intake grille is located just below the discharge grille, and it con-
sists of two vaned grilles. Both sets of vanes should be fully open during operation of the air conditioner in any mode,
except when outside air is being drawn in. The opening or closing of the vanes is controlled by operating tabs projecting
from the left side of the left grille and the right side of the right grille.
c. Fresh air damper. The fresh air damper, which can be opened to adjust outside air through the rear of the air con-
ditioner, is controlled by knobs on each end of an operating shaft: One knob just below the middle of the evaporator in-
take grille, and the other in a similar position in the back of the unit. The knobs are marked for the proper direction to
turn for open or close. It is often desirable to keep the fresh air damper partially open during all modes of operation to
add enough fresh, outside air to the conditioned room to prevent constant recirculation of stale air.
2-3. Covers.
a. Deflector doors. (See Figure 1-3). The deflector door is located above the round condenser fan guard at the
bottom of the rear surface of the air conditioner. The door encloses the condenser coil, and helps to seal out cold air,
rain or snow during the heating season. During the cooling season, the open deflector door prevents recirculation of
heated exhaust air into the condenser coil area. The deflector door must be open during operation of the air conditioner
in the cooling mode.
2-1
